Are the 1‑2 mm superficial, mobile nodules on the posterior scalp of a 13‑day‑old infant consistent with milia rather than pilar (trichilemmal) cysts?

Milia vs Pilar Cyst in a 13-Day-Old Infant

The 1–2 mm superficial, mobile nodules on the posterior scalp of a 13-day-old infant are consistent with neonatal milia, not pilar (trichilemmal) cysts. 1

Key Distinguishing Features

Size and Age Strongly Favor Milia

• Milia in neonates are typically 1–2 mm in diameter, appearing as small white-yellow superficial cysts that are extremely common in newborns 1, 2
• Pilar cysts range from 5–20 mm or larger and are exceedingly rare in neonates, typically presenting in adults with a female predominance 3, 4
• The 13-day age of this infant makes pilar cyst virtually impossible, as these lesions arise from mature hair follicle epithelium and develop over years 4, 5

Clinical Characteristics

• Palpation should confirm superficial, non-fixed, cystic consistency for milia diagnosis 1
• Milia are keratin-containing dermal cysts that resolve spontaneously within the first few months of life 2
• Pilar cysts are deeper dermal lesions that grow slowly over prolonged periods and do not spontaneously resolve 4, 6

Critical Anatomic Consideration

Before labeling these as benign milia, you must verify the exact anatomic location to exclude midline spinal involvement. 1

• Any midline posterior scalp or spinal lesion in a neonate warrants urgent MRI and neurosurgical consultation within days, as approximately 70% of neonates with midline cutaneous markers have underlying congenital spinal cord malformations 1
• Even posterior scalp lesions require careful assessment to ensure they are truly lateral and not midline 1

Management Protocol for Confirmed Milia

Immediate Management

• No active treatment is required; milia are self-limited and resolve spontaneously over weeks to months 1
• Routine well-child visits are sufficient for isolated milia without concerning features 1

Parent Counseling

Instruct parents to monitor for the following red flags and seek immediate care if present: 1

• Rapid growth or increase in number
• Color change (especially darkening or redness)
• Bleeding or ulceration
• New neurologic symptoms

Indications for Dermatology Referral

Refer to dermatology if: 1

• Lesions persist beyond 3–6 months
• Rapid increase in number or size
• Atypical color, texture, or behavior develops
• Diagnostic uncertainty remains

Common Pitfalls to Avoid

• Do not confuse with infantile hemangiomas, which typically present within the first 2–3 weeks as red, raised lesions with rapid proliferation—not soft, mobile, white-yellow cysts 1, 7
• Do not assume all posterior scalp lesions are benign; always verify non-midline location to avoid missing spinal dysraphism 1
• Avoid unnecessary biopsies or ablative procedures for typical neonatal milia, as these are self-resolving 1